Recycling chains for lithium-ion batteries: A critical examination of current challenges, opportunities and process dependencies.

Lithium-ion batteries (LIBs) show high energy densities and are therefore used in a wide range of applications: from portable electronics to stationary energy storage systems and traction batteries used for e-mobility. Considering the projected increase in global demand for this energy storage technology, driven primarily by growth in e-vehicles, and looking at the criticality of some raw materials used in LIBs, the need for an efficient recycling strategy emerges. In this study, current state-of-the-art technologies for LIB recycling are reviewed and future opportunities and challenges, in particular to recover critical raw materials such as lithium or cobalt, are derived. Special attention is paid to the interrelationships between mechanical or thermal pre-treatment and hydro- or pyrometallurgical post-treatment processes. Thus, the unique approach of the article is to link processes beyond individual stages within the recycling chain. It was shown that influencing the physicochemical properties of intermediate products can lead to reduced recycling rates or even the exclusion of certain process options at the end of the recycling chain. More efforts are needed to improve information and data sharing on the exact composition of feedstock for recycling as well as on the processing history of intermediates to enable closed loop LIB recycling. The technical understanding of the interrelationships between different process combinations, such as pyrolytic or mechanical pre-treatment for LIB deactivation and metal separation, respectively, followed by hydrometallurgical treatment, is of crucial importance to increase recovery rates of cathodic metals such as cobalt, nickel, and lithium, but also of other battery components.

X-ray fluorescence sorting of non-ferrous metal fractions from municipal solid waste incineration bottom ash processing depending on particle surface properties.

A heavy non-ferrous metal fraction (< 50 mm) of municipal solid waste incineration bottom ashes from wet-mechanical treatment was separated by screening, magnetic separation and eddy-current separation into ferrous metals, non-ferrous metals and residual sub-fractions. The non-ferrous metal fractions were divided and subjected to (i) a washing process, (ii) dry abrasion and (iii) no mechanical pre-treatment to study the effect of resulting different surface properties on a subsequent X-ray fluorescence sorting into precious metals, zinc, copper, brass, stainless steel and a residual fraction. The qualities of the X-ray fluorescence output fractions were investigated by chemical analyses (precious metal fraction and the residual fraction), pyrometallurgical tests and subsequent chemical analyses of the metals and slags produced by the melting processes (zinc, copper, brass and stainless steel fraction). Screening directs brass and stainless steel primarily into the coarser fractions, while copper and residual elements were rather transferred into the finer fractions. X-ray fluorescence sorting yielded zinc, copper, brass, stainless steel and precious metals fractions in marketable qualities. Neither a negative nor a positive impact of mechanical pre-treatment on the composition of these fractions was identified. Solely the yield of the brass fraction in the grain size 16-20 mm decreased with increasing mechanical pre-treatment. The pre-treatment also had no impact on yield and quality of the products of pyrometallurgical tests.

Recycling of waste printed circuit boards with simultaneous enrichment of special metals by using alkaline melts: A green and strategically advantageous solution.

The increasing consumption of electric and electronic equipment has led to a rise in toxic waste. To recover the metal fraction, a separation of the organic components is necessary because harmful substances such as chlorine, fluorine and bromine cause ecological damage, for example in the form of dioxins and furans at temperature above 400°C. Hence, an alternative, environmentally friendly approach was investigated exploiting that a mixture of caustic soda and potassium hydroxide in eutectic composition melts below 200°C, enabling a fast cracking of the long hydrocarbon chains. The trials demonstrate the removal of organic compounds without a loss of copper and precious metals, as well as a suppressed formation of hazardous off-gases. In order to avoid an input of alkaline elements into the furnace and ensuing problems with refractory materials, a washing step generates a sodium and potassium hydroxide solution, in which special metals like indium, gallium and germanium are enriched. Their concentrations facilitate the recovery of these elements, because otherwise they become lost in the typical recycling processes. The aim of this work was to find an environmental solution for the separation of plastics and metals as well as a strategically important answer for the recycling of printed circuit boards and mobile phones.

Property Criteria for Automotive Al-Mg-Si Sheet Alloys.

In this study, property criteria for automotive Al-Mg-Si sheet alloys are outlined and investigated in the context of commercial alloys AA6016, AA6005A, AA6063 and AA6013. The parameters crucial to predicting forming behavior were determined by tensile tests, bending tests, cross-die tests, hole-expansion tests and forming limit curve analysis in the pre-aged temper after various storage periods following sheet production. Roping tests were performed to evaluate surface quality, for the deployment of these alloys as an outer panel material. Strength in service was also tested after a simulated paint bake cycle of 20 min at 185 °C, and the corrosion behavior was analyzed. The study showed that forming behavior is strongly dependent on the type of alloy and that it is influenced by the storage period after sheet production. Alloy AA6016 achieves the highest surface quality, and pre-ageing of alloy AA6013 facilitates superior strength in service. Corrosion behavior is good in AA6005A, AA6063 and AA6016, and only AA6013 shows a strong susceptibility to intergranular corrosion. The results are discussed below with respect to the chemical composition, microstructure and texture of the Al-Mg-Si alloys studied, and decision-making criteria for appropriate automotive sheet alloys for specific applications are presented.